Lighting unoccupied spaces such as rooms and corridors is a major source of wasted energy in many commercial and residential buildings. Even where convenient switches are provided to deactivate unused lights, the occupants of a building may not remember to turn the lights off, or may not choose to do so. In addition, for safety reasons, it is often desirable that the lighting in a room should be activated automatically whenever that room is occupied.
One known solution for this problem is to use presence detectors, such as passive infra red sensors, to automatically activate and deactivate lighting systems as required. For example, a hallway may be provided with a presence detector which activates the lights whenever a person steps into the hallway. Once the hallway is again unoccupied, the presence detector will deactivate the lights to save power.
However such detectors are typically installed as part of a complete lighting system. The presence detector is typically installed in a recess in the wall or ceiling at the same time as the light fittings (luminaires) are installed and connected to the lighting controller for the lighting system. Such presence detectors are also difficult to move once installed, meaning that if there is a change in the layout of a room, the presence detectors may be rendered useless until they are reinstalled elsewhere, at considerable cost of time and effort.
In view of the above, presence detectors which can be installed in a pre-existing lighting system and are easily movable would be desirable.